In order to observe the effects of earlier sea ice melting on zooplankton, field observations were conducted in the northern Bering Sea, located in the Arctic region, by the training ship Oshoro-Maru (see figure ①) in 2017 when sea ice melting was as usual and in the summer of 2018 when sea ice melting was earlier, respectively. Zooplankton samples were collected using a NORPAC net (see figure ②), fixed in formalin immediately after collection, and brought back to the laboratory. In the land-based laboratory, zooplankton were counted by taxon and species under a stereomicroscope. The dominant copepods (see figure ③) were counted at each developmental stage*2.
